Twenty homes were evacuated after a gas leak caused a fire in Cwmbran, Torfaen.
Fire crews were called at 1830 BST on Thursday to what was reported to be a refuse fire but found that a gas main had ignited.
Quarter of an hour later, the gas leak stopped itself, creating a gas cloud. A 200m exclusion zone was set up and homes evacuated.
People living nearby were asked to keep windows and doors closed. The incident was over by 2100 BST.
South Wales Fire and Rescue Service said people were then allowed back into their homes.
Wales and West Utilities, who are responsible for the gas supplies, isolated the leak to stop any further release of gas.